The 29-year-old midfielder, who joined Leeds on loan from Stoke in September, has made 22 appearances for Neil Warnock's side, who have won five of their last six npower Championship matches.
"I'm gutted it's finished," said Tonge, whose contract at Stoke expires at the end of the season. "Obviously I can't play now until something's sorted because my loan has finished now.
"When you're on a roll you want to keep playing and hopefully the lads will keep playing like that and getting the points. I wanted to keep playing, but it's the way it works with 93 days.
"When I first came here we were thin on the ground with injuries, but now there's competition all over and that gets an extra 10% out of people. If we can keep that together, we'll make a challenge."
Tonge, who began his career at Sheffield United and made almost 300 first-team appearances under then Blades boss Warnock, added on Leeds' official website: "We've beaten some good sides and we know what we can do.
"We just need to keep going. We're desperate to get in the top six and I'm desperate to come back and help the lads, so fingers crossed."